JPH06122991A - Tin-zinc alloy electroplating bath - Google Patents

Abstract

PURPOSE:To form an Sn-Zn alloy plating layer of uniform composition at all times in a wide plating current density range by adding a specified amphoteric surfactant to the conventional Sn-Zn alloy electroplating bath. CONSTITUTION:An amphoteric surfactant of imidazoline, betaine, alanine, gylicin or amide type is added by 1-10g/l to a 1-cyan plating bath contg. stannous sulfate, etc., as the tin ion source and zinc sulfate, etc., as the zinc ion source. An Sn-Zn alloy plating layer of uniform composition is stably formed regardless of the change in current density on the surface of a metallic member of intricate shape on which the plating current density tends to lack uniformity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tin-zinc alloy electroplating bath, and in particular, a tin-zinc alloy which can stably form a plating having a uniform alloy composition without being affected by the current density. Regarding electroplating bath.

[0002]

2. Description of the Related Art Tin-zinc alloy electroplating has been attracting attention in recent years as an industrial plating for automobile parts, electronic parts, etc. because of its excellent corrosion resistance, salt water resistance, solderability, etc., and has been widely used. . As a plating bath used for this tin-zinc alloy plating, an alkaline cyanide bath, a pyrophosphoric acid bath, a fluorinated bath, a sulfonic acid bath, a carboxylic acid bath, a nocyanic alkali bath, etc. are proposed, and some of them are put into practical use. Has reached. A common drawback of conventional tin-zinc alloy plating baths is that the alloy composition of the plating is strongly affected by current density. That is, even if the plating condition is set to a certain current density, the locally observed current density distribution in each surface portion of the material to be plated is not necessarily the same, and the distribution is non-uniform. It becomes uneven. This phenomenon is particularly remarkable in the case of a material having a large plating area or a material having a complicated shape. As a result, the performance of the plating or the quality of the plated product,
That is, variations occur in corrosion resistance, chromate film conversion, solderability, and the like. Therefore, as a plating bath that is less affected by the current density, a citric acid bath that uses a water-soluble luster additive obtained by reacting a reaction product of an aliphatic amine and an organic acid ester with phthalic anhydride (Japanese Patent Publication No. 57- 27
95) has been proposed and put into practical use. In addition, it is 57-
Japanese Patent No. 2796 proposes a tin-zinc alloy plating bath containing a specific amount of tin sulfate and zinc sulfate and adding citric acid (salt) and ammonium sulfate or sodium. Further, JP-B-59-48874 proposes a tin-zinc alloy plating bath in which a specific polymer is added to citric acid (salt) or ammonium salt. However, even when plating is performed with these baths, the alloy composition of the plating in the very low electric part has a high tin content and the uniformity of the alloy composition is insufficient. Therefore, in the present situation, it is inevitable to deal with the situation of equipment or strict work management.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a plating bath capable of obtaining a film of good quality such that the tin-zinc plating alloy composition is constant over a wide range of current densities. It is in.

[0004]

The present invention was made based on the finding that the above problems can be efficiently solved by adding an amphoteric surfactant to a conventional tin-zinc plating bath. That is, the present invention provides a tin-zinc alloy electroplating bath characterized by containing an amphoteric surfactant.
In the present invention, the tin-zinc alloy electroplating bath may contain an arbitrary amount of an amphoteric surfactant, but the amount is from 0.01 to 3
It is preferable to contain 0 g / l, more preferably 0.3
~ 15 g / l. That is, if it is less than 0.01 g / l, the effect is not sufficient, and if it exceeds 30 g / l, bubbling during plating, reduction in current efficiency, etc. occur. Examples of the amphoteric surfactant include imidazoline type, betaine type, alanine type, glycine type and amide type amphoteric surfactants. Among these, those having a structure represented by the formula 1 are preferable as the imidazoline type amphoteric surfactant.

[0005]

[Chemical 1](In the formula, X is a halogen, a hydroxy group, a sulfuric acid group or
C₁~ C_TenHydroxyalkane sulfonic acid group, hydro
Xycarboxylic acid group, R¹Is C₈~ C₂₀Alkyl group of R
²Is a C containing a hydroxy group₁~ C_FiveAn alkyl group of
R³Is C₁~ C _TenCarboxylic acid, sulfonic acid or
Or their salts and sulfate salts. ) Also,
Structure represented by Formula 2 as a tine-type amphoteric surfactant
Those having are preferred.

[0006]

[Chemical 2] (In the formula, R ⁴ is a C _{8 to} C ₂₀ alkyl group, R ⁵ and R ⁶
May be the same or different and each represents a C ₁ -C ₄ alkyl group. )

As the alanine-type amphoteric surfactant, those having a structure represented by the formula 3 or 4 are preferable. ^{_{R 7 -NHCH 2 CH 2 COONa (}} 3) R 7 -NH (CH 2 CH 2 COONa) 2 (4) ( wherein, R ⁷ is an alkyl group of C ₈ ~C _20.) Glycine type amphoteric surfactants As the activator, one having a structure represented by Formula 5 or Formula 6 is preferable. ^{_{R 8 -NHCH 2 CH 2 NHCH 2}} COOH (5) (R 8 -NHCH 2 CH 2) 2 NCH 2 COOH (6) ( wherein, R ⁸ is an alkyl group of C ₈ ~C _20.) Amide type As the amphoteric surfactant of, those having a structure represented by formula 7 are preferable. R ⁹ —CONHCH ₂ CH ₂ NHCH ₂ COONa (7) (In the formula, R ⁹ is a C _{8 to} C ₂₀ alkyl group.) These amphoteric surfactants may be used alone or in combination of two or more. Good.

The tin-zinc alloy electroplating bath of the present invention includes an alkali cyanide bath, a pyrophosphoric acid bath, a fluorinated bath,
Examples thereof include a silicofluoride bath, a sulfonic acid bath, a carboxylic acid bath, a non-cyanic alkaline bath, a gluconic acid bath, and an organic acid bath. Usually, stannous salt such as stannous sulfate is used as metal tin in an amount of 1 to 100 g / l, preferably 5 to 50 g / l, zinc salt such as zinc sulfate is used as metallic zinc in an amount of 0.2 to 80 g / l,
A bath containing 25 to 40 g / l is preferable, and a no-cyan bath is particularly preferable. Also, there, a citric acid bath,
A carboxylic acid such as a gluconic acid bath may contain 40 to 400 g / l, or pyrophosphoric acid may contain 30 to 300 g / l, or sulfamic acid may contain 40 to 400 g / l, and the pH may be 3 to 10. . Further, 0.1 to 20 g / l of a conventional brightening agent or additive, for example, a water-soluble brightening agent obtained by reacting a reaction product of an aliphatic amine and an organic acid ester with phthalic anhydride may be added. it can. Using the plating bath of the present invention, metals such as iron, nickel, copper and their alloys can be plated with any tin-zinc alloy,
For example, plating with a thickness of 0.5 μm to 0.5 mm can be applied, and tin-zinc alloy plating with a wide range of compositions can be applied by changing the ratio of tin and zinc in the plating bath. For example, a zinc content of 5 to 15% by weight is used for electrical contacts, and a zinc content of 15 to 45% by weight is used for the purpose of salt water resistance and corrosion resistance. For good coatings, the zinc content is 55 to 10% by weight. The plating conditions may be arbitrary, but the plating bath temperature is preferably 10 to 40 ° C. and the current density is 0.1 to 10 A / dm ² . After plating using the plating bath of the present invention, chromate treatment can be carried out by a conventional method. At this time, use chromate treatment
It can be carried out by the method described in JP-A-8-1110.

[0009]

EFFECTS OF THE INVENTION The tin-zinc alloy plating bath of the present invention has a uniform alloy composition for deposition over a wide range of current density, so that even a material having a complicated shape can be plated with a uniform alloy composition. In addition, the chromate film can be sufficiently formed. As a result, the plating performance is improved, the product is stabilized, and the productivity is improved, and a high quality tin-zinc alloy plating film can be provided.

[0010]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples, and the composition of the plating bath and the plating conditions can be arbitrarily changed according to the purpose. Example 1 Table 1 shows the tin-zinc alloy plating basic bath used in the examples of the present invention.

[Table 1] Table 1 Basic plating bath used in Examples Bath type Citric acid bath Gluconic acid bath Pyrophosphate bath Bath stannous sulfate 40g / l Stannous sulfate 40g / l Stannous pyrophosphate 20g / l Group Zinc sulfate 40g / l Zinc sulfate 40g / l Zinc pyrophosphate 40g / l formed citric acid 100 g / l gluconate 120 g / l pyrophosphate 100 g / l ammonium sulfate 80 g / l ammonium sulfate 80 g / l pH sodium hydroxide potassium hydroxide tone or or integer aqueous ammonia aqueous ammonia agent plating bath temperature: citric acid Bath and gluconic acid bath 25 ° C. Pyrophosphoric acid bath 60 ° C. In this example, an iron plate was used as the cathode and a tin-zinc alloy plate was used as the anode, and the bath temperature was 10-5 at a current density of 0.2-5 A / dm ² .
Electroplating was performed for 0 minutes. Table 2 shows the tin-zinc alloy plating baths containing the amphoteric surfactant used in the examples of the present invention and the alloy compositions of the platings obtained from these baths. As a comparative example, Table 2 also shows the plating baths containing no amphoteric surfactant and the alloy compositions of the plating obtained from these baths.

[0011]

[Table 2] Table 2 Plating bath and alloy composition of the obtained plating Plating Plating Amphoteric surface active agent No. Basic bath type Bath pH Nominal addition amount 1 Citric acid bath 6.0 Coconut oil alkyl-N-carbo 5 g / l Xyethyl-N-hydroxyethyl imidazolium betaine sodium 2 Citric acid bath 6.0 Coconut oil alkyl-N-carbo 5 g / l Xyethyl-N-hydroxyethyl imidazolium betaine sodium 3 Citric acid bath 9.0 Stearyldimethylammoni 1 g / l umbetaine 4 Citric acid bath 5.0 Cetyl di (aminoethyl) 10 g / l glycine Na salt 5 citric acid bath 5.0 cetyl di (aminoethyl) 1 g / l glycine Na salt 6 citric acid bath 6.0 lauric acid amide 1 g / l propylbetaine 7 citric acid bath 6.0 lauric acid amide 1 g / l Propylbetaine 8 citric acid bath 6.0 Pentadecanoic acid amide 10 g / l Propylbetaine 9 citric acid bath 7.0 Undecylami Noethyl 5 g / l carboxylic acid Na salt 10 citric acid bath 7.0 undecylaminoethyl 5 g / l carboxylic acid Na salt 11 gluconic acid bath 3.0 2-myristyl-1-carbo 2 g / l xymethyl-1-hydroxypropyl imidazolinium Mubetaine 12 gluconic acid bath 6.0 2-myristyl-1-carbo 2 g / l xymethyl-1-hydroxypropyl imidazolinium betaine 13 pyrophosphate bath 9.0 lauryl diethylaminoacetic acid 5 g / l betaine 14 citric acid bath 6.0 2-cetyl- 1-Carboxyme 1 g / l Cyl-1-hydroxypropyl imidazolinium betaine 15 citric acid bath 7.5 lauryl diethylammonium 2 g / l betaine 16 citric acid bath 5.0 lauryl-N-hydroxyethyl 5 g / l ru-N- Sulfoethyl imidazolinium betaine 31 Citric acid bath 6.0 No-32 Citric acid bath 9.0 No-33 Ruconic acid bath 3.0 None-34 Gluconic acid bath 6.0 None-35 Pyrophosphate bath 9.0 None-36 Citric acid bath 6.0 None-37 Citric acid bath 7.5 None-

Table 2 (continued) Alloy composition of plating; zinc content (%) Other additives Negative electrode Current density No. Nominal addition amount Plating appearance 0.2A / dm ² 1.5A / dm ² 5A / dm ² 1 None-matte 31.2 40.3 43.0 2 Aromatic aldehyde 0.1 g / l Semi-gloss 28.0 38.6 39.2 3 None-Matte 25.5 38.8 41.2 4 None-Matte 20.7 35.6 34.7 5 Dip sole 0.1 g / l Semi-gloss 20.1 35.1 35.7 DG-FR-7 6 No-matte 21.3 38.4 39.4 7 Dip sole 8 ml / l Semi-gloss 20.5 35.1 38.5 SZ-240S 8 No-matte 27.0 37.6 41.0 9 No-〃 21.5 34.9 37.7 10 Dip sole 8 ml / l Semi-gloss 19.3 34.4 38.2 SZ-240S 11 Polyoxyethylene laurylamine 5 g / l Semi-gloss 20.5 35.9 39.3 (Ethylene oxide 15 mol added) 12 None-matte 23.3 36.6 39.0 13 None-semi-gloss 25.0 38.9 40.5 14 Aliphatic amine And organic 2ml / l semi-gloss 10.3 11.8 12.3 acid ester and no It reaction product 15 of the full barrel acid - matte 54.6 68.6 74.6 16 epoxy compound and flop 2 g / l Semi-gloss 67.9 80.3 82.4 B reaction products of propylene glycol 31 Deippusoru 8 ml / l Semi-gloss 12 35 37.5 SZ-240S 32 Dip sole 8 ml / l Semi-gloss 9.0 48.3 50.6 SZ-240S 33 Polyoxyethyle 5 g / l Semi-gloss 8.5 17.0 33.8 N-laurylamine (addition of 15 moles of ethylene oxide) 34 Polyoxyethyle 5 g / l Semi-gloss 9 35 45 N-laurylamine (addition of 15 mol of ethylene oxide) 35 None-Full surface sponge ----- Deposition 36 Aliphatic amine and organic 2 ml / l Semi-gloss 8.4 15.0 19.7 Acid ester and phthalic anhydride the reaction product 37 polyethylene glycol 5 g / l semi-gloss 18.1 40.2 51.9 Lumpur with

In the table, Nos. 1 to 16 are Examples and 31 to 37 are Comparative Examples. Further, the amounts of tin and zinc in the baths of Nos. 14, 15, 16, 36 and 37 (g / l: as metals) are as follows.

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[Procedure amendment]

[Submission date] December 3, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

The tin-zinc alloy electroplating bath of the present invention includes an alkali cyanide bath, a pyrophosphoric acid bath, a fluorinated bath,
Examples thereof include a silicofluoride bath, a sulfonic acid bath, a carboxylic acid bath, a non-cyanic alkaline bath, a gluconic acid bath, and an organic acid bath. Usually, 1 to 100 g / l, preferably 5 to 50 g / l, of stannous salt such as stannous sulfate as metal tin, and 0.2 to 80 g / l of zinc salt such as zinc sulfate as metal zinc.
1, a bath containing 25 to 40 g / l is preferable, and a non-cyan bath is particularly preferable. In addition, 40 to 400 g of carboxylic acid in a citric acid bath, a gluconic acid bath, etc.
1 or 30 to 300 g / l of pyrophosphoric acid or 40 to 400 g / l of sulfamic acid,
The pH can be 3-10. Further, 0.1 to 20 g / l of a conventional brightening agent or additive, for example, a water-soluble brightening agent obtained by reacting a reaction product of an aliphatic amine and an organic acid ester with phthalic anhydride may be added. it can. Using the plating bath of the present invention, iron, nickel,
Metals such as copper and their alloys can be plated with any tin-zinc alloy plating, for example 0.5 μm to 0.5 mm thick, and the tin-zinc ratio in the plating bath can be changed. Thus, tin-zinc alloy plating having a wide range of compositions can be applied. For example, a zinc content of 5 to 15% by weight is used for electrical contacts, and a zinc content of 15 to 45% by weight is used for the purpose of salt water resistance and corrosion resistance. For good coatings, the zinc content is 55 to 90 % by weight. The plating conditions can be arbitrary, but the plating bath temperature is 10 to 4
It is good to carry out at 0 ° C. and a current density of 0.1 to 10 A / dm ² . After plating using the plating bath of the present invention, chromate treatment can be carried out by a conventional method. At this time, the chromate treatment can be performed by the method described in Japanese Patent Publication No. 38-1110.

Claims (1)

[Claims] 1. A tin-zinc alloy electroplating bath containing an amphoteric surfactant.